I have just ordered Canon 400mm F5.6L lens for wildlife and bird photography , but when i am done after my ordering now , many were saying in different forums that 300mm F4 is better in IQ than 400mm prime.. Is it ? I checked with my dealer and he said that canon india has already shipped my order and now i cant change my order .. Can anyone please pass on some advise to me ? Is canon 400mm prime good lens or did i just messed up completely? Price difference between two lens is around $200 (my wife will kill me , if i upgrade) but i really wanted to know your suggestions/advises soon on this.

Both were reviewed at PhotoZone. If you need the reach of a 400mm lens then the 400mm compares well with the 300mm plus extender. Enjoy your new lens and ignore forum chatter, CameraLabs excepted of course.

Bob.

P.S. I make it a point only to read positive reviews after I've made a purchase! If I do happen across a less than glowing report I quite naturally assume the author is an idiot!!

The truth is that the qualitative differences between these two lenses are so small that there is no practical difference.

That doesn't stop the cognoscenti from waving MTF charts at you and insisting you should always shoot at a particular aperture, regardless of the subject. The vast majority of those people have little practical experience.